This item first appeared in August 20,2009, but I think it is so important to reprint the article in light of todays interest in streetcars and light rail in Vancouver and Surrey. The LR55 rail, not only provides a cheaper solution to tram track construction, it makes a quick job of construction, making life a lot easier for those living next to the new tramline. A 20 km. BCIT to UBC tramline could be laid in as many as 125 days (two track gangs) or a little more than 4 months!
One of the major expenses of conventional tram projects is the track. This is laid on a concrete raft set under the road. In order to accomodate these rafts the underground services, like gas and water, have been diverted out of the way of the tracks. This process took a considerable amount of time and money in schemes like Manchester and Sheffield. In addition it caused disruption to inhabitants while taking place.
To avoid or reduce these problems NET proposes to use the revolutionary LR55 rail system. This is laid in the road structure itself so that there is little or no disturbance to underground services. Instead a slot is cut in the road and the track laid in. The track exploits the strength of existing highway pavements by transmitting the static and dynamic loads from the upper surface, rather than the foot of the rail as in conventional track. This results in the load on the railhead being distributed onto the sub-base of the highway, being of a sufficiently low value not to require a separate foundation. Up to 100m can be laid in a night.
The track system consists of three main components:-
- LR55 Rail
- The rail carries the weight of the tram, steers the tram and is the return conductor for the electric power supply. The LR55 rail has a wide lip compared to conventional tram rail. This is to allow the road structure to carry the weight of the tram. The rail top surface and the trough unit are treated to provide a compatible skid resistance to the adjacent highway surface.
- Elastomeric Grout
- This is a rubber like compound that prevents vibrations from the tram being transfered to the road and surroundings. Old fashioned trams used to rumble along the street as the tracks did not have this feature. Modern trams are very quiet because of features like this grout. It also insulates the electricity returning to the sub station, so that it does not travel through other cables buried in the road.
- Precast Trough Unit
- This forms the base for the rail and connects it to the road structure. It is fitted into a slot cut into the road.
Where there is a road base thicker than 225mm the Trough Unit is bedded into the base.
Where the road base is less than 225mm the Trough Unit is bedded onto the sub-base.
The track can also be laid in concrete pavements, older road construction and block paving. These are outlined in the technical specification for the track.
Should it be necessary to work on services crossing the tramway, the track is self-supporting over a distance of one metre. This allows access trenches to be dug without affecting the tram service. Safe methods of working have been developed to ensure the safety of tramway passengers and staff, as well as utility workers. These methods are already established in existing tram schemes.
There are further details of LR55 track at the LR55 web site.
For more information on LR55 for our more technical visitors: